forget to do sth. 意思是忘記做某事了,這事沒做,forget doing sth.意思是忘記曾經做過某事,這事做了但不記得做過了。例句: Don't forget to lock the door when you leave. 你走時別忘了鎖門。
I forgot telling him about it, so I told him again.我忘了告訴過他這件事了,所以又和他説了一遍。